The invention concerns a barrel of thermoplastic material.
It will be noted here that the term barrel is used herein in a broad sense to embrace various forms of barrel-like container including drums, casks and the like.
A barrel is subjected to various requirements in regard to the structure and performance thereof, of which hitherto those which have been considered to be most important are an adequate level of resistance to the effects of external forces, for example due to shocks, blows or stresses due for example to the barrel being dropped. Those aspects have to be taken into account in designing the barrel configuration.
A barrel of typical design is generally provided with rings which extend around the barrel and which are disposed at a spacing from the upper and lower ends respectively, for more convenient handling of the barrel. It may also be necessary for a plurality of barrels to be stacked one upon the other so that the upper and lower ends of each barrel must provide a sufficient stable surface on which the barrel can stand and can also support another barrel. For that purpose, the upper end of the barrel, which has a connecting or nozzle portion defining an emptying opening, may have a generally trough-like depression in which the connecting or nozzle portion is accommodated, whereby the upper end of the barrel provides the required support surface. That arrangement also provides that the projecting connecting or nozzle portion, by virtue of being accommodated in the depression, is substantially protected from the effects of external forces acting on the barrel.
In regard to taking account of environmental requirements, increasing attention is now also being paid to the requirement that a barrel of that kind can be totally emptied in order to ensure that any residual amounts of the contents of the barrel, which still remain therein after the barrel has been emptied, cannot pass uncontrolledly into the environment and thus give rise to pollution.
However, arranging the connecting or nozzle portion of the barrel, as referred to above, within a trough-like depression, gives rise to the disadvantage that, when the barrel is in the usual inclined position adopted for emptying thereof, the inside surface of the barrel includes regions, beside the trough-like depression configuration, which are lower in that position of the barrel than the lowest region of the barrel emptying opening, on the inside wall surface of the barrel. Therefore, in order to ensure that a barrel or like container is emptied as completely as possible, the connecting or nozzle portion may be arranged closely adjacent to the wall of the barrel so that, when the barrel is in the usual inclined position for emptying thereof, on the inside of the barrel there are no points which are lower than the lowest region, on the inside of the barrel, of the generally round emptying opening of the barrel. However, arranging the connecting portion in the immediate vicinity of the side wall of the barrel in that way in turn gives rise to the difficulty that, even when the connecting or nozzle portion is disposed in a trough-like depression in the upper end part of the barrel, the connecting or nozzle portion is less protected against forces which act on the barrel from the exterior thereof, laterally in relation thereto. That consideration applies both in regard to forces which act directly on the connecting portion and also in regard to loadings which act on the edge or the side wall of the barrel and which are produced for example in the event of the barrel dropping from a considerable height. The resulting deformation of the edge or rim of the barrel or the side wall thereof inevitably also affects the connecting portion of the barrel and the region of the upper end part of the barrel which carries the connecting portion, thus giving rise to stress peaks in that region which can result in splits and other damage to the barrel.
Those difficulties could be reduced for example by arranging the barrel in such a way that the connecting portion extends into the interior of the barrel by a certain amount. That provides that on the one hand the upwardly projecting part of the connecting portion can be shorter while on the other hand the depth of the depression which accommodates the connecting portion can be reduced whereby the surface area available for external forces to act thereon can be decreased. In that case the inwardly extending part of the connecting portion must be sufficiently long to provide a sufficiently firm fit for a closure plug or stopper which is screwed into the connecting portion and more specifically into a female screwthread provided therein for that purpose. It will be appreciated however that that part of the connecting portion which extends into the interior of the barrel constitutes on the inside of the barrel a shielding or screening means around the emptying opening so that after emptying of the barrel the barrel still contains an amount of the previous contents thereof, which depends on the axial extent of the part of the connecting portion which projects into the interior of the barrel. It is not possible for a barrel with a connecting portion of that kind to be completely or almost completely emptied.
EP-A-0 291 695 discloses a barrel provided with such a connecting portion, wherein the part thereof which projects into the interior of the barrel has openings therein which extend as far as the inner boundary wall of the trough-like depression. In that way the residual material left in the barrel can flow towards the emptying opening of the barrel without the inwardly extending part of the connecting portion representing a screening means around the emptying opening, to prevent material from flowing therethrough. However connecting portions of that kind must be fitted to the finished barrel in the form of separate components so that the junction can under some circumstances represent a weak point which could be damaged or caused to fail in the event of the barrel being subjected to the influence of considerable external forces. Furthermore the design configuration of that connecting portion involves an increased level of production cost which can have an effect on the economy of the barrels which are usually produced in large numbers. In addition, with a barrel of that design configuration, in order to provide for emptying which is as complete as possible, the trough-like depression must be so designed that the surface area of the upper end part of the barrel, which serves as a support surface, is accordingly reduced.